The signaling circuit of a telephone station has traditionally been locked by a mechanical device. Rotary dial telephones are often locked by connecting a cylinder to a finger hole in the rotary dial. A key is then inserted in the cylinder to unlock and remove the cylinder from the rotary dial. Pushbutton telephones are often locked by connecting a cover over the pushbutton keypad. A key is then inserted in the cover to unlock it and remove it from the keypad.
Computer controlled locking arrangements have also been used. With such an arrangement a computer controlled telephone central office or other switching system uses class of service restrictions to lock the signaling circuit of a connected telephone. Computer controlled restriction arrangements are also used to prevent computer terminals from accessing unauthorized programs and data. Under such an arrangement passwords, access codes or identification numbers are assigned to the terminals of their users and the proper password, access code or identification number must be transmitted to the connected computer before the terminal can access restricted programs or data. However, these computer controlled locking or restriction arrangements require administration of class of service codes, passwords, access codes or identification numbers by a central computer and they do not inhibit operation of the telephone or computer terminal.
The present invention overcomes this requirement through use of a locking circuit located within the telephone station.